1. Field of the Invention
This invention relates to methods of manufacturing a GaP light emitting element substrate, and more precisely to a substrate (hereafter referred to as "GaP red light emitting element substrate") comprising a plurality of GaP layers formed on a GaP single crystal substrate which is used to manufacture GaP light emitting elements, and methods of manufacturing it.
2. The Prior Art
Light emitting elements such as light emitting diodes are obtained normally by layering a plurality of semiconductor layers on a semiconductor single crystal substrate to prepare a multi-layer semiconductor element substrate with a pn junction, and making it into elements. Of these, GaP red light emitting elements can be obtained by using a GaP red light emitting element substrate prepared by forming one or more layers of n-type and p-type GaP layers, one after another, on an n-type GaP single crystal substrate.
GaP has the indirect transition-type band structure, and it does not emit red light when a pn Junction is simply formed. Therefore, the p-type GaP layer(s) is doped with zinc (Zn) and oxygen (O) to form Zn-O pairs, which would be the emitting centers, in the p-type GaP layer(s). This GaP light emitting element emits red light which peak wavelength is approximately 700 nm.
As described thus far, the p-type GaP layer(s) of the GaP red light emitting element substrate is doped with Zn and O, and a higher Zn-O pair concentration would give light emitting elements with higher luminance. In order to do this, it is necessary to dope a large amount of O in this layer(s). However, there was a problem in that doping of a large amount of O gave rise to many precipitates of gallium oxide (Ga.sub.2 O.sub.3) on and/or in the surface of the p-type GaP layer of the light emitting element substrate manufactured by the liquid phase epitaxial growth method, resulting in an increase in the ratio of surface failure due to the Ga.sub.2 O.sub.3 precipitates.